Single or double storey extension: which is right for your home?

Both can transform a home. We compare space, cost, planning and disruption to help you choose.

A single storey extension is the classic way to create a bigger kitchen or family room. A double storey extension adds bedrooms or a bathroom upstairs too. Here’s how they compare.

Foundations and roof are among the biggest costs of any extension. A second storey shares them, so the cost per square metre is often lower, even though the total is higher.

Single storey rear extensions are more likely to fall under permitted development. Two storey extensions face tighter limits and more often need a planning application, particularly where they affect neighbours’ light or privacy.

A double storey extension means opening up the first floor as well, so there’s more disruption upstairs. Good planning and sequencing keep this to a minimum.